Set rosidl_typesupport_introspection_{c,cpp}_identifier target visibility public

[udaya2899]

Why?

A cc_binary we have that transitively depends on ros2_rosidl and when ran inside an oci_container, fails with

error while loading shared libraries: librosidl_typesupport_introspection_c_identifier.so: cannot open shared object file: No such file or directory

To add the expected .so files to the container as a layer, we need the target that directly builds these .so files. For this, we need the visibility to be public.

PS: Thanks in advance for your work in maintaining this. Btw, looking forward for Bzlmod support soon!